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The following is an excerpt from City Parks, Clean Water, a report by the Trust for Public Land’s Center for City Park Excellence that examines the role of urban parks in managing stormwater. This is the seventeenth installment in a series of 19 posts.

Installing natural stormwater controls within a park is not inexpensive and is usually not a quick process. But the relevant comparison of costs and impacts must be made against any typical park improvement project, as well as against traditional gray approaches, which are usually much more expensive and take far longer. How much a water-smart park costs and how long it takes to build depends on innumerable factors of geography, geology, weather, bureaucratic rules and, often, city and neighborhood politics. Nothing about urban water management is easy, but the evidence shows that the natural approach is more economical.

A survey of 20 stormwater park projects in 13 states, carried out by The Trust for Public Land, illustrates the variety of forms a water management project can take, as well as the relative cost effectiveness of green versus gray infrastructure. The parks ranged in size from half an acre to more than 300 acres, with stormwater management features ranging from only a small corner of some facilities to the whole park in others. The median size of the parks is 8 acres, and the median size of the stormwater portion is 2.5 acres. The following charts compare some of the costs of traditional gray infrastructure vs. green infrastructure in selected projects.

(The Trust for Public Land)

(The Trust for Public Land)

The selected projects encompass a total of 713 acres and cost $771 million to build, although most of the land and much of the spending was not related to stormwater management. Where financial breakdowns were available, the median cost of green infrastructure construction was about $174,000 per acre. Annual operating cost in 2014, when known, had a midpoint of about $10,800 per acre. The approval, funding, design, and construction of stormwater parks took a median of 5 years to complete, which is not significantly more than the time required for a traditional park. In the case of especially complex projects , which may get tied up in lawsuits or political wrangling, this process may span a decade or more, but on the other hand some projects, such as the conversion of an asphalt New York City schoolyard, may take less than two years.

There are some creative ways for cities to fund their water-smart parks, and these may include partnerships and combinations of funding sources. The distribution of the benefits and costs of green infrastructure can be uneven, so the question of who should pay can be complicated and controversial. Every city seemingly handles the issue differently, and the financial landscape is not static. In some places, water and sewer utilities have no experience partnering with other agencies on projects, leaving the park department to take the first step in finding synergy between improving parkland and cleaning waterways.

In other locales, such as Cleveland, the situation is reversed, with the sewer district taking the initiative. In Cleveland’s case, the sewer district needs to aggressively reduce sewage overflows into Lake Erie to meet the obligations of its consent decree with the EPA. To do so, the District is using a combination of gray and green infrastructure techniques to capture, hold, store, and infiltrate stormwater. Fortunately, land is available, and in a few cases parks have also been utilized for larger ponds.

In an area on Cleveland’s east side with many vacant properties and severe overflows, a public-private partnership devised an ambitious urban agriculture and green infrastructure program. The project includes new storm sewers and street catch basins, plus four bioretention ponds, the largest of which is dug out of a former playing field in Otter Park. The field was replaced with amended soils and a thick stand of native plants, and an underdrain will slowly release the stormwater to a nearby piped stream. The partnership is also building an outdoor classroom with pervious pavement, native plantings, and demonstration rain gardens to help educate tour groups and park visitors of the importance of stormwater management. Cleveland is also aggressively publicizing the fact that controlling stormwater and cleaning Lake Erie will enable residents to use more of their lakefront parks more of the time. Maintenance of the green and gray infrastructure in Otter Park, as well as the outdoor classroom, will be a sewer district responsibility in perpetuity.